Process for preparing alkali metal pyrithione and its polyvalent metal complexes from pyridine oxide

摘要

The present invention generally relates to a novel process for preparing alkali metal pyrithione from pyridine N-oxide, using a sulfurination agent and a base agent. In particular, the present invention relates to an efficient process for preparing polyvalent metal complexes of sodium pyrithione from the alkali metal pyridine N-oxide described herein.

主权项

1. A process for preparing an alkali metal pyrithione comprising the steps of:
adding pyridine N-oxide, at least one sulfurination agent and at least one base agent to a solvent blend, the solvent blend containing a surfactant and a first organic solvent, to form a first reaction mixture; wherein the sulfurination agent and the base agent are added in a predetermined molar ratio relative to the pyridine N-oxide; heating the first reaction mixture to a first predetermined temperature; cooling the first reaction mixture to a second predetermined temperature; adding an aqueous solution to the cooled reaction mixture to form a two phase liquid having an organic layer and an aqueous layer; filtering the aqueous layer or the two phase liquid to obtain a filter cake and a filtrate; separating the aqueous layer from the two phase liquid before or after filtering; sparging the aqueous layer or the filtrate with a chemically inert gas into a trap, the trap comprising an alkali metal hydroxide to form a second reaction mixture; and isolating the alkali metal pyrithione from the second reaction mixture.